1. Technical Field
The present invention relates to a circuit for controlling a switching time of a transmitting and receiving signal in a wireless communication system, and more particularly, to a circuit for controlling a switching time of a transmitting and receiving signal in a wireless communication system, capable of being used in various wireless communication systems by adjusting an RC time constant of an N-type metal oxide semiconductor (NMOS) switch used in a high frequency switch circuit.
2. Description of the Related Art
An example of a scheme used in a portable wireless communication system includes an extended global system for mobile communications (EGSM) scheme and a digital cellular system (DCS) scheme that are mainly used in Europe, a global system for mobile communications 850 (GSM850) scheme and a global system for mobile communications 1900 (GSM1900) scheme that are mainly used in the United States, a personal digital cellular (PDC) scheme that is mainly used in Japan, and the like. However, due to the recent rapid popularization of a cellular phone, system users have not been satisfied in a frequency band allocated to each system particularly in large cities of advanced countries. For example, a problem such as connection difficulty, disconnection during a call, or the like, has been generated.
Therefore, as a countermeasure for solving this problem, a method of allowing users to use a plurality of systems to promote an increase in a substantially available frequency and expanding a server user zone or effectively utilizing communication infrastructures of each system has been suggested.
Meanwhile, due to the development of a wireless communication industry, radio frequency (RF) components such as a low noise amplifier, an oscillator, a high output amplifier, a switch, and the like, manufactured by an integrated circuit technology have been developed in various applications such as a mobile phone, a wireless local area network (WLAN), and the like. In accordance with the development of the wireless communication industry, a use frequency band has also been raised and an RF component operated in a frequency of an X band or more has been demanded.
An example of a switch operated in a high frequency band such as a microwave, or the like, includes a single pole double through (SPDT) switch. A general SPDT switch uses a field effect transistor (FET) based element. At the time of designing the SPDT switch, an FET element having a large area is generally used as a serial switching element in order to reduce insertion loss, and an FET element having a relatively small area is used as a switching element connected in parallel with the serial switching element in order to improve isolation characteristics.
Research into improving performance of the SPDT switch has been variously conducted according to an application. For example, there are an SPDT switch using a parallel resonator in order to remove a parasitic component to improve isolation and reflection loss, an SPDT switch including an impedance converting circuit added between switching elements in order to certainly short-circuit and open impedance in a turn-on and turn-off state of the switching elements, and the like. Particularly, the latter case adopts a structure capable of obtaining high isolation and low insertion loss; however, it basically includes a filter structure, such that it has narrow band characteristics. Therefore, the latter case has a limited application and is difficult to use.